Experimental Physics, Saarland University, D-66041 Saarbrücken, Germany.
J Phys Condens Matter. 2011 May 11;23(18):184109. doi: 10.1088/0953-8984/23/18/184109. Epub 2011 Apr 20.
We present, along with some fundamental concepts regarding imbibition of liquids in porous hosts, an experimental, gravimetric study on the capillarity-driven invasion dynamics of water and of the rod-like liquid crystal octyloxycyanobiphenyl (8OCB) in networks of pores a few nanometers across in monolithic silica glass (Vycor). We observe, in agreement with theoretical predictions, square root of time invasion dynamics and a sticky velocity boundary condition for both liquids investigated. Temperature-dependent spontaneous imbibition experiments on 8OCB reveal the existence of a paranematic phase due to the molecular alignment induced by the pore walls even at temperatures well beyond the clearing point. The ever present velocity gradient in the pores is likely to further enhance this ordering phenomenon and prevent any layering in molecular stacks, eventually resulting in a suppression of the smectic phase in favor of the nematic phase.
我们提出了一些关于液体在多孔介质中吸收的基本概念，同时还进行了一项实验，研究了水和棒状液晶辛氧基氰基联苯（8OCB）在单块二氧化硅玻璃（Vycor）中几纳米大小的孔网络中毛细驱动力侵入动力学。我们观察到，与理论预测一致，对于两种被研究的液体，都存在着与时间的平方根相关的侵入动力学和粘性速度边界条件。对 8OCB 的温度依赖自发吸收实验表明，由于分子在孔壁的诱导下排列，即使在远远超过清亮点的温度下，也存在向列相。在孔中始终存在的速度梯度可能会进一步增强这种有序现象，并防止分子堆积的分层，最终导致向列相取代更有利于形成层状结构的近晶相。
